Secondary battery.



To all when 'it maq concern:

UNITED STATES PATENT OFFICE.

WILLIAM MORRISON, OF CHICAGO, ILLINOIS, ASSIGNOR 0F ONE-THIRD TO M. A.

I LUMBARD, OF DES MOINES, IOWA.

SECONDARY BATTERY.

Specification of Letters I'atent.

No drawing. Application filed June 20,1902, Serial No. 112,472 Renewed May 22, 1908. Serial No. 497,714.

Be it known that I, WILLIAM Monnrson, a

citizen of the United States of America, and resident of the city of Chicago, county of look, State of Illinois, have invented a certain new and useful Improvement in Secoudary Batteries, of which the following is a specification.

My invention relates to electric accumulator-soisecondary batteries of that type in which the negative and positive elements are immersed in an alkaline solution containing zinc, and commonly called zincate of potash or soda.

In charging, the'zinc in the solution is de-' posited upon the positive element, and during the discharge of the battery the zinc then leaves the positive element and returns to the solution, this process being repeated in the continued charge and discharge.

The principal object of my invention is to provide means for more effectively preventing local action, and thus provide a battery which may be allowed to remain on open circuit for a considerable length of time. In batteries of this type, the zinc of the solution is deposited, by electrolysis, upon a metal support. It is essential that this support shou d have as little weight as possible, and should be of maximum rigidity and strength. To prevent local action between the metal support and the deposited zinc it has been the custom'to amalgamate this metal support. But the metal of the support must not only be rigid and light, but it must also be capable of practically preventing the mercury.

from penetrating beyond its subjacent surface, or, in other words, from penetrating into its interior mass, because should the mercury thus penetrate into the interior mass it will render the su port brittle and thus make it liable to breali and destroy its capacity to resist buckling. When, however, the mercury is amalgamated upon the surface of the metal su port, it will not remain,- uniformly upon t e surface in the discharge, but tends to run off the sup ort, leaving thewhole, or parts, of the sur ace of the support exposed to the solution. Therefore to provide a -more' com lcte and efficient means for uniforml an securely holding the amalgam upon t to entire surface of the support, fixedly, uniforml and seeurely, to more completely prevent ocal action, some extremely porous, or absorptive, substance must be coated over, or upon, the surface of the sup ort, which covering should be capable of a sorbing, or taking up into its mass, a large quantity of the mercury. This porous coating, upon the surface of the support, must not only be capable of taking up, or absorbing into its mass, at large uantity of the mercury, but it must also be of low potential relative to the zinc, that is, the difference of potential between the material constituting the absorptive and amalgam-holding coating of the zinc, must be slight, or as small as possible. And finally both the support, and particularly the amalgam-holding coating, should be relatively insoluble in the solution.

I have found in practice that copper provides a good material for the sup )ort, and I prefer to use it; but iron or nicl rel may be used, or in fact any metal which will not permit the )enetration of the mercury to any materia degree may be used, provided it is practically insoluble in the solution and has suflicient rigidity. For instance, brass is not a good material fora support because it is composed of an alloy of zinc and copper and the mercury penetrates beyond the subjaccnt surface of its mass rendering it brittle.

For'the aumlgam-holding or absorptive -coatiug after practical experience, I have ascertained that cadmium is admirably adapted for the purpose. This cadmium is capable of absorbing and taking up. uniformly and into and through the body of its mass, a relatively large quantity of mercury, and when the cadmium containing themercury is coated over and upon the surface of the support, the cadmium firmly and securely binds and holds the mercury upon the support, thereby preventing the mercury from running off the sup ort and providin means for more eltective y preventing loca action between the support and the zinc, and

as the support is of a character to prevent the penetration of the mercury its Strength is not diminished. 'lhat local action ismore ollcctively prevented is evident because the zinc is do osited upon a coating of cadmium, thoroughly assimilated with mercury and the material of the coating is thus completelly amalgamated. It is ObVIOUS thiLt the ca mium itself cannot be used as a su port, becauseof its capacity to readily a sorb the mercury into its interior mass. I his penetration and assimilation of the mercury renders the cadmium too brittle for use as a support. 4

, The negative element can be of any suitable known or approved substance. The positive element, however, consists preferably of a foraminous or perforated or woven copper support having a coating of cadmium or cadmium and mercury, although a support having a'plain surface may be employed if desired. In preparing the positive element the cadmium can be first applied to this support and the'mercury can then be applied to the coating of cadmium, or both can be applied together. I have found it best to deposit the cadmium on the support by electrolysis. And the mercury may also be applied in this way. And this may bedonc by providing a suitable anode, and a copper support as a cathode, immersed in a saturated solution of sulfate of cadmium, and during the passage of a suitable electric current, the cadmium Q r I $425,243

' 1. In a secondary battery, an electrolyte of alkaline zincate, a support coated with cadmium upon which support the zinc of the electrolyte is to be deposited and a suitable negative electrode.

. 2. In a secondary battery, an electrolyte of alkaline zincate, a support coated with cadmium and mercury upon which support the zinc of the electrolyte is to be deposited and a suitable negative electrode.

cury, and amino deposit on said. coating.

4. In a secondary battery, the combination of a support coated with cadmium and mercury, an electrolyte containing zinc, and a sultable negative electrode.

' 3. In a secondary battery, the combination of a support coated with cadmium and mer- Signed by me at Chicago Illinois this 18th day of June 1902.

WILLIAM MORRISON. Witnesses CHAS G. BU-LKLEY, WM. A. Hannnus. 

